I don't "get" how a program can update itself. How can I make my software update?

Question

Say I make an .exe file and everything is peachy. Wonderful it works.

Say I worked on a new feature on the software and I want it to be available for people who already have the older version, how can I make the software find my new version, patch it, and then go about it's business.

I can't seem to wrap my head around the issue.

Thank you.

EDIT: I'm sorry for the confusion, but I was meaning a more code-wise answer. Is there something special in my code I should have to allow updating?

For example, if I want to add a new feature, how can I add a "method" to an already packaged .exe? :S That has me in a swivel.

Answer 1

A popular solution is to actually have a separate process replace the necessary files.

Have you ever noticed that Firefox has to restart whenever it updates? Well, that is because a separate process (updater.exe) is downloading the files, closing firefox, replacing the files, and then starting firefox again.

edit of course this assumes you're hosting a list of updates online that the updater program can check (an RSS feed, or even a simple text file).

Answer 2

Usually the process is as follows:

• the user starts the applicataion
• the application launches an "updater" (another program)
• the updater retrieves from the Internet if a newer version exists
• if that's the case, propose the user to update
• the users accepts, the updater downlads the new install package (that can be incremental)
• the updater shuts the application down (or better, asks the user to do it) and launches the new installer.
• the installation package do the rest

Of course you can have many variation, but this is the basic way to do it.

On Windows, at least, some software install an updater deamon that is always on and checks for new updates of the software it takes care (GoogleUpdater, for example).